Lubricant stabilized by bis alkylene



.of boron.

United States Patent O LUBRICANT STABILIZED BY'BIS ALKYLENE PYROBORATEGlenn E. Irish, Detroit, Mich., assignor to Ethyl Corporation, New York,N.Y., a corpnration of Delaware No Drawing. Application May 3, 1956Serial No. 582,606

3 Claims. (Cl. 25249.6)

This invention relates to improved hydrocarbon lubricants and moreparticularly to hydrocarbon lubricants stabilized by a his alkylenepyroborate.

Hydrocarbon lubricants deteriorate when subjected to the elevatedtemperatures encounted in lubrication service. This deterioration leadsto deleterious deposits of carbonaceous material on the lubricatedsurfaces which greatly reduce the eliectiveness of the lubricant.

It is, therefore, an object of this invention'to provide improvedhydrocarbon lubricants. Another object is to provide improvedhydrocarbon lubricants containing stable esters of pyroboric acid. Afurther object of this invention is to provide improved hydrocarbcnlubricants having a high degree of thermal stability. Another object isto provide an improved crankcaselubricating oil containing a hisalkylene pyroborate.

The above and other objects of this invention are accomplished byproviding a hydrocarbon lubricant containing a stabilizing amount ofboron as a bis alkylene ester of pyroboric acid. The resulting lubricanthas a greatly enhanced thermal stability. Pyroboric acid may berepresented by the formula:

and the corresponding bis alkylene esters have the formula:

where R is analkylene group of from 2 to 6 carbon atoms in length andwhich contains from 2 to about 20 carbon atoms. Thus, R can represent asubstituted alkylene group of from 2 to 6 carbon atoms in length whichcontains alkyl, aryl, cycloalkyl, aralkyl, alkaryl, halogen, ketone,carboxyl, or other substituents. These substituents may contain up to 18carbon atoms when the alkylene group contains two carbon atoms, butsubstituents having up to about 8 carbon atoms are preferred as theygive an ester of lower molecular weight, and thus more boron per mole.Alkyl substituents of from 1 to 6 carbon atoms are particularlypreferred because the esters containing these groups are more easilyprepared.

When a bis alkylene pyroborate is compounded with a crankcaselubricating oil, it is desirable to add a small amount, i.e., suflicientbis alkylene pyroborate to form a composition containing from 0.001 to1.0 weight percent However, a preferred embodiment of this inventioncomprises a crankcase lubricating oil containing from about 0.01 toabout 0.15 weight percent boron as a bis alkylene pyroborate as it hasbeen found that these amounts of boron effectively increase the thermalstability. A particularly preferred embodiment of this inventioncomprises a liquid hydrocarbon crankcase lubricating oil containing from0.01 to 0.15 weight percent boron as bis(2-methy1-2,4-pentylene)pyroborate.

The bis alkylene pyroborate esters used in the practice of thisinvention may be prepared from boric acid, H BO and an aliphatic diol,by first converting the boric acid to metaboric acid, HOBO, and thenreacting the metaboric acid with an equimolar amount of the diol underconditions such that 1.5 moles of water are removed from the reactionmixture for each mole of diol reacted.

The process of preparing bis alkylene pyroboratesis carried out in anappropriate solvent which is inert to both the reactants and products ofthe reaction and which forms a minimum boiling azeotrope with water.These solvents ordinarily have boiling points of from C. to thedecomposition temperatures of the reactants and products of thereaction. Appropriate solvents include aliphatic and aromatichydrocarbons and organic compounds containing elements other than carbonand hydrogen. Examples of suitable solvents include toluen benzene,xylene, dioxane and cyclohexane.

Further embodiments of this invention are illustrated by the followingexamples in which all parts are by weight unless otherwise stated. 1

EXAMPLE I Preparation of metaboric acid To the toluene-metaboric acidsolution prepared in Example I, containing 43.8 parts of HOBO, was added118.2 parts'of 2-rnethyl-2,4-pentanediol. The resulting mixture wasagain heated with stirring to the boiling,

temperature of the toluene water azeotrope until an amount of azeotropecorresponding to 27 parts of water had been removed from the reaction'mass. The remaining toluene was removed by distillation atatmosphericpressure leaving a water-white liquid having a boiling point of 114 to115 Cat 2 millimeters of mercury. The molecular weight of this productwas determined to be 267 and on analysis the product was found to have54.6% of carbon, 9.2% hydrogen, 8.12% boron and, by difference, 28.01%oxygen. This corresponds to a calculated analysis of 53.4% carbon, 8;96%hydrogen, 8.02% boron and 29.62% oxygen and a calculated molecularweight of 269.95 for bis(2-methyl-2,4-pentylene) pyroborate having theformula:

CH3 CH3 H-( 30 045E nn B-o-m on, H3C-(IO/- 1 O--CCHt i m. The refractiveindex of this compound is 1.43180 n EXAMPLE III Seventy-six parts ofpropylene glycol were added to a toluene-metaboric acid solution,prepared as described in Example I, and reacted according to theprocedure described in Example II. The reaction was discontinued afteran amount of toluene-water azeotrope corresponding to 27 parts of waterhad been removed from the reaction vessel. On removing the toluenebyatmospheric distillation, 143 parts of bis propylene pyroborate, awater-white liquid, remained in the reaction vessel.

EXAMPLE IV The procedure of Example III is followed except that 118parts of hexanediol-2,5 is reacted with metaboric acid in lieu ofpropylene glycol, to prepare bis(2,5-hexylene) pyroborate.

EXAMPLE V Following the procedure of Example II, 104.1 parts ofpentanediol-1,5 is reacted with 43.8 parts of metaboric acid to preparebis(l,5-pentylene) pyroborate.

EXAMPLE VI A solution of metaboric acid and xylene was prepared from61.8 parts of boric acid and 215 parts of xylene according to theprocedure in Example I. To this solution is added 62 parts of ethyleneglycol and the mixture is heated until an amount of xylene waterazeotrope, amounting to 27 parts of water, is removed. Atmosphericdistillation of the remaining xylene enables recovery of a good yield ofhis ethylene pyroborate.

The lubricants which are beneficially enhanced by the practice of thisinvention include those fractions or blends of fractions from mineraloils which are used for lubricating and related purposes. Lubricatingoil stock is usually considered to include all the distillate obtainablefrom crude oils after the lower boiling fractions and gas oils have beenexpelled, as well as some of the residues that are left in the stillwhen non-asphaltic crudes are distilled.

Generally, lubricating oils are made from distilled fractions of acrude, but often these distilled fractions are combined with refinedresiduum, such as bright stocks, to yield oils having excellentlubricating qualities.

Lubricating oils are made into literally thousands of products which mayconsist of the pure mineral oils or blends containing one or more otheringredients. Among these products are motor oils, aviation oils, machineoils, transformer oils, cable oils, turbine oils, cutting oils, loomoils, textile oils, etc. Greases are lubricating oils which have beenrendered solid or semi-solid by the addition of soaps or similarmaterials. Typical embodiments of this invention comprising a bisalkylene pyroborate and a hydrocarbon lubricant are illustrated by thefollowing examples.

EXAMPLE VII To 500 parts of a commercially available neutral crankcaselubricating oil was added 2.8 parts of bis- (2-methyl-2,4-pentylene)pyroborate, a quantity sufficient to produce a composition containingabout 0.05 weight percent boron. The mixture was agitated until the bis-(2-methyl-2,4-pentylene) pyroborate was completely dispersed in the oil.

EXAMPLE VIII To 10,000 parts of a wholly-distilled mixed base, solventrefined lubricating oilhaving a gravity of 28.9 API, a viscosity gradeof SAE 10W-20 and a viscosity index of 135.7 is added 2.75 parts ofbis(l,5-hexadecalene) pyroborate and the mixture is stirred until thepyroborate is dissolved in the oil.

EXAMPLE IX To 1000 parts of a mixed base solvent-refined lubricating oilcontaining bright stock and which has an SAE viscosity grade of 20, anAPI gravity of 30.5 and a viscosity index of 107.4, is added 16.75 partsof bis- (l,5-pentylene) pyroborate.

EXAMPLE X To 2162 parts of a wholly distilled lubricating oil having anAPI gravity of 303, a viscosity index of 154.2 and an SAE number of5W-20, is added 1.6 parts of bis ethylene pyroborate and the mixture isstirred until the ester is dissolved.

EXAMPLE XI To 216 parts of a wholly distilled lubricating oil having anAPI gravity of 29.1, an SAE number of 10W-30 and a viscosity index of138.9, is added 21.4 parts of bis(3-methyl-1,3-butylene) pyroborate. Themixture is agitated until the pyroborate has dissolved.

EXAMPLE XII To 1,000 parts of the oil described in Example VII is added15 parts of bis(l,2-eicosylene) pyroborate and the mixture is agitateduntil the pyroborate is dissolved.

EXAMPLE XIII To 1,000 parts of the oil described in Example VIII isadded 10 parts of bis(l,6-hexylene) pyroborate.

EXAMPLE XIV To a lubricating grease consisting of 11 parts of aluminumstearate, 1 part of lithium stearate and 88 parts of an oil having aviscosity of seconds Saybolt Universal at 100 F., is added 2 parts ofbis(2-methyl-2,4-' pentylene) pyroborate and the mixture is blendeduntil the ester is completely dispersed through the grease.

To demonstrate the superiority of a crankcase lubricating oil of thisinvention containing a his alkylene pyro' borate, comparative tests wererun on the oil prepared according to Example VII and the identical oilwhich did not contain any bis(2-methyl-2,4-pentylene) pyro-' borate.These oils were compared by the Panel Coker' Test which measures theoxidative stability of a lubricating oil at a hot metal surface. Thistest is described in the Aeronautical Standards group of the departmentsof Navy and Air Force specification MIL-L-7808c dated November 2, 1955.In this instance the tests were run at 550 F. The results of the testsare summarized in Table I. These data illustrate that a lubricating oilcontaining a small amount of a his alkylene pyroborate has a greatlyreduced coking tendency at elevated temperature when compared to anidentical oil containing none of the pyroborate esters. Thus, the oilcontaining a pyroborate ester has a greatly enhanced thermal stabilityand a superior resistance to oxidative deterioration.

TABLE I Panel coker test In addition to the his alkylene pyroborates,the hydrocarbon lubricants of this invention may contain otheradditives. These other additives may include for example, viscosityindex improvers, detergents, corrosion inhibitors, metal deactivators,rust inhibitors, color stabilizers, pour depressants, emulsifiers, dyes,etc., and in the case of greases metallic soaps, fillers, etc.

The diols suitable for use in preparing the pyroborate esters of thisinvention include those wherein the by droxyl groupsare' separated byfrom 2 to 6 carbon atoms. Examples of the pyroborate esters which areprepared from these diols include: his ethylene pyroborate, bis-(l,3-pro'pylene) pyroborate, bis'(1,4-butylene) pyroborate,bis(l,5-pentylene) pyroborate, bis(l,2-heptylene) pyroborate,bis(l,3-butylene) pyroborate, bis(l-rnethyl-l.2- propylene) pyroborate,bis( 1,3 pentylene) pyroborate, bis(25-hexylene) pyroborate,bis(2-methyl-2,4-pentylene) pyroborate,bis(2-methyl-4,4-diethyl-l,2-pentylene) pyroborate,bis(6-n-propyl-1,4-nonylene) pyroborate, bis- (l,2-eicosylene)pyroborate, bis(3,5-diethyl-3,5-hexylene) pyroborate,bis(2-chloro-3,5-pentylene) pyroborate, bis- .roborate having theformula wherein R is an alkylene group of 2 to 6 carbon atoms in lengthand containing 2 to about 20 carbon atoms.

2. An improved liquid hydrocarbon crankcase lubricating oil containingfrom about 0.001 to about 1.0%

of boron as a liquid bis alkylene pyroborate having the formula whereinR is an alkylene group of 2 to 6 carbon atoms is length and containing 2to about 20 carbon atoms.

3. An improved liquid hydrocarbon crankcase lubrieating oil containingfrom about 0.001 to about 1.0%

of boron as liquid bis (2-methyl-2,4-pentylene) pyroborate having theformula References Cited in the file of this patent UNITED STATESPATENTS 2,721,181 Lawrence Oct. 18, 1955 2,741,548 Darling Apr. 10, 19562,795,548 Thomas June 11, 1957

1. A HYDROCARBON LUBRICANT CONTAINING FROM ABOUT 0.001 TO ABOUT 1.0% OFBORON AS A LIQUID BIS ALKYLENE PYROBORATE HAVING RHE FORMULA